The ISM (industrial, scientific and medical) radio bands are license-exempt bands, which were originally reserved internationally for the use of radio frequency (RF) energy for industrial, scientific and medical purposes other than communications. However, in recent years these bands have also been shared with license-free error-tolerant communications applications such as Wireless local area networks (WLAN) and cordless phones in the 915 MHz, 2.450 GHz, and 5.800 GHz bands. A main usage on these ISM bands is ‘WiFi’.
‘WiFi’ is not a technical term. However, the WiFi Alliance has generally enforced its use to describe only a narrow range of connectivity technologies including wireless local area network (WLAN) based on the IEEE 802.11 standard, which is a set of standards carrying out WLAN communication in the 2.4, 3.6 and 5 GHz frequency bands (cf. document [1]).                ISM band 2.4 GHz (WiFi 802.11b and 802.11g/n)        ISM band 5 GHz (WiFi 802.11a/n/ac)        
Recent growth in data traffic driven by mobile applications on smart phone devices, tablets, etc. has continued to strain the capacity of today's networks. Therefore, network operators are increasingly utilizing un-licensed WiFi spectrum to cope with such network congestion, and this trend is expected to accelerate further as traffic demand continues to grow.
Use of unlicensed spectrum is a cost-effective mean to add the needed capacity of today's networks, given the limited availability and high cost of licensed spectrum. Currently, WLAN is integrated as a separate access network to the 3GPP EPC (3rd Generation Partnership Project Evolved Packet Core). This requires extra cost of deploying the complete WLAN access network and also impacts the 3GPP core network entities. Existing WiFi offload solutions are based on this deployment model of distinct 3GPP and WLAN access networks using a common core with selective switching of flows based on operator/user policies. Other solutions are possible that result in a tighter integration and aggregation of 3GPP access network components with WLAN access networks without any impact to and reusing the same 3GPP core network elements.
It was firstly proposed in a discussion paper and Study Item (SI) proposal in RAN#53 (cf. documents [2] and [3]), which propose that the study may involve extending the same design principles already defined for carrier aggregation to support aggregation/coordination of cells/carriers across Wide and Local Area Networks as well.
There was another SI proposal in RAN#57 named “WLAN/3GPP Radio Interworking”, which gains almost all companies' support (cf. document [4]). The objectives of the study are to evaluate LTE-WLAN and UTRA-WLAN interworking procedures addressing the issues above while improving seamless and non-seamless mobility.
Further, some small cell discovery and PDCH design aspects are discussed in document [5].